Air cushion for pneumatic pruning shears



R. H. DROMAN AIR CUSHION FOR PNEUMATIC PRUN ING SHEARS Dec. 3, 1957 Filed June 14, 1955 2 Sheets-Sheet 1 ATTORNEYS R. H. DROMAN AIR CUSHION FOR PNEUMATIC PRUNING SHEARS Dec. 3, 1957 2 Sheets-Sheet 2 Filed June 14, 1955 \w s 0 m L Nu Q v Q 1 N VENT OR [Pane/[H.flzmm QZI M, wwzw/y ATTORNEYS Patented Dec. 3, 1957 AIR CUSHION FOR PNEUMATIC PRUNING SHEARS Russell Hobart Droman, Gasport, N. Y.

Application June 14, 1955, Serial No. 515,423

3 Claims. (Cl. 121-38) This invention relates to orchard equipment, and more particularly to an improvement for reducing piston impact in a pneumatic pruning shears.

Heretofore, the actuation of pneumatic orchard equipment has been accompanied by a rapid succession of mechanical impacts or shocks which have caused a serious shortening of the life of the equipment as well as an inordinate breakage rate. In addition to these detrimental effects, the repetitive series of impacts has caused the use of such pneumatic tools to fatigue the operator thereof after fairly short periods of operation. This invention contemplates a means and method for substantially minimizing and eliminating the series of mechanical impacts which have previously characterized the operation of such pneumatic orchard equipment.

Accordingly, therefore, a primary object of this invention is to provide an arrangement for substantially redncing impact in a pneumatic pruning shears.

Another object of this invention is to provide an mproved means for cushioning a pneumatic piston at the end of its stroke to eliminate damaging impact to the parts of a pneumatc system.

Still another object of the invention is to provide a novel piston and cylinder structure with means for providing diiferent rates of absorbing impact-energy on opposite sides of the piston.

A further object of this invention is to provide means for absorbing piston shock in a pruning shears by using air cushioning.

A still further object of this invention is to provide a method and means for providing dissimilar deceleration rates on opposite sides of the piston used in a pruning shears.

Other and further objects will become apparent from the following detailed description and drawings which form a part of this specification and in which like numerals indicate like parts, and in which:

Figure 1 represents a side elevation of a pneumatic pruner which embodies a preferred form of the invention.

Figure 2 represents a plan view of a pneumatic pruner which embodies a preferred form of the invention.

Figure 3 represents an enlarged longitudinal sectional view taken along the line 3-3 in Figure 2, and indicating a fragmentary portion thereof.

Figure 4 represents a sectional view taken along the line 4-4 of Figure 3.

Turning now to the drawings, and more particularly to Figure 1, there is shown a pneumatic pruning shears provided with a fixed blade 1 having a movable blade 2 pivotally mounted thereupon. An internally threaded cylinder 3 which is pivotally secured to the movable blade 2 is threadedly engaged by one end of a pull-rod 4. A jam nut 5 is positioned on the pull-rod 4 to tightly abut the end of cylinder 3, and lock said pull-rod securely thereto.

The other end of the pull-rod 4 enters the housing 6, and is actuated therein by means presently to be described. The housing 6 enters and terminates within an elongated upper flange 7 which is pierced by a plurality of axially extending studs 8.

The studs 8 penetrate the periphery of a lower flange 9. Flanges 7 and 9 are provided with a flat inner surface. A thin-walled cylinder 10 is positioned between the upper and lower flanges, and nuts 11 are provided, one on each end of the studs 8 to permit the tightening of said upper and lower flanges and the rigid positioning of said cylinder therebetween. Each of the flanges is provided with an annular shoulder on its periphery, as shown most clearly in Figure 3. The cylinder 10 fits within said annular shoulders, and abuts an annular gasket to form an airtight sea].

A handle-piece 12 engages the lower flange 9, and bolts 13 are provided to penetrate and rigidly secure said handle-piece to the flange. The engagement of the lower flange, and the bolts affixing said handle-piece 12 thereto are shown more clearly in Figure 2, as is the positioning of the cylinder 10 between the upper and lower flanges 7 and 9 respectively. The placement of the studs 8 in the periphery of said flanges, is also shown in Figure 2.

Continuing with the detailed description, in Figure l and 2 a first threaded coupling 14 engages the upper flange 7, and a second threaded coupling 15 engages the lower flange 9. Between the couplings 1415 a length of tubing 16 is connected.

Referring now to Figure 3, it will be observed that the first threaded coupling 14 has access to the interior of cylinder 10, by way of a port 17 located in the upper flange 7. Similarly, the second threaded coupling 15 is connected to communicate with the port 18 located in lower flange 9. The ports 17 and 18 alternately function as either intake or exhaust ports, depending upon circumstances explained more fully below.

Under certain circumstances the ports 1718 may function to supply input air, via tube 16, to the interior of the end of cylinder 10 which abuts flange 7. The functioning of these ports in supplying air to the end of said cylinder, as well as exhausting air therefrom, will become apparent as the specification proceeds.

The lower flange 9 is also provided with port 19. It will be observed that the ports 18 and 19 are effectively divided by a trigger actuated valve 20. The valve 20 is engaged by a trigger 21 which is pivotally secured to the lower flange 9. The ports 1819 are provided with orifices 22--23, respectively, thus providing access to a supply of compressed air supplied to the interior of handle-piece 12 by way of a suitable hose and coupling (not shown) which threadedly engage the tapped hole 24.

Within the cylinder 10 there is located an actuating rod 25 provided with a threaded portion 26. The actuating rod 25 is journaled within the bore of the upper flange 7 and the housing 6, and is pivotally secured to the pullrod 4 to actuate same and operate the movable blade 2, in a manner well known to those skilled in the art.

Within cylinder 10, mounted upon the actuating rod 25 and concentric therewith is the piston assembly which includes compression cups 27a and 27b separated by a spacer-disc 28. it will be observed that each compression cup is provided with an axially extending peripheral flange, and that the flanges on the two cups extend in opposite directions.

Between one side of the spacer-disc 28 and compression cup 27a a first flexible cup 29a is located. Conversely, a second flexible cup 29a is mounted between the opposite side of disc 28 and the compression cup 27b. Both flexible cups are proportioned to tightly engage the inner walls of the cylinder 10, and may be fabricated of rubber, leather, or other suitably resilient material.

Also mounted upon the actuating rod 25, and substantially concentric therewith, is a first sleeve 30a which abuts the compression cup 27a. A second sleeve'30b is similarly mounted upon the rod 25 and abuts the compression cup 27b. Sleeves 30a and 30b are not threaded, but fit snugly over rod 25. A flat disc 31a is inwardly slidably mounted upon the sleeve 30a, and urged away from the cup 27a by a coiled compression spring 32a interposed between said disc and said cup. A disc 31b is similarly mounted on sleeve 30b and is repelled from cup 27b by means of spring 32b mounted concentrically with said sleeve 30b, as shown. The disc 31a is positioned by means of a nut 33a which threadedly engages the rod 25 and abuts one face of said disc 31a; conversely, the disc 31b is positioned by the nut 33b which threadedly engages rod 25 and abuts said disc 31b. It will be readily observed that the degree of tension on either of the springs 32a or 32b may be individually adjusted by means of the nuts 33a and 33b.

In operation, when the trigger is released as shown in Figure 3, compressed air is permitted to flow through the orifice 23, and completely through the port 19 by traversing the hole 34 in the valve 20. Since port 19 enters the interior of chamber 10, the actuating rod and its associated parts are urged towards the opposite end of the cylinder. Exhaust air on the other side of the piston is permitted to traverse the port 17, tubing 16, and the port 18. Since, however, the port 18 registers with a bleed-hole 35 which exhausts to atmosphere (not shown) a path for dispelling exhaust air is readily available.

The bleed-hole 35 may exhaust to atmosphere by registry with an aperture in the lower flange 9 or by any other suitable means.

When the actuating rod 25 moves forward suificiently, the disc 31a engages the flat inner surface of the upper flange and by covering the port 17, halts the exhaust of air from the cylinder. Then, for the remainder of the stroke, the spring 32a is compressed until the peripheral flange, a shoulder on cup 27a, engages the flat disc 31a. This materially assists in damping the shock which normally accompanies the end of the stroke. Additionally, the air trapped between the end of the cylinder and the oncoming piston absorbs kinetic energy by being compressed. The retardation oflered by the compression of the trapped air within the chamber gives rise to a cushioning effect, and substantially reduces the shock which ordinarily would attend the sudden stop of the piston assembly.

When the trigger 21 is depressed, hole 36 in valve 20 is caused to register with the port 18. Then, compressed air is supplied via tube 16, and port 17 to the end of cylinder which abuts the upper flange. This, of course, urges the piston assembly towards the lower flange.

Since the depression of trigger 21 has moved a. bleedhole 37 into registry with the atmosphere, the air trapped between the piston assembly and the lower flange is exhausted, via port 19 in bleed-hole 37, to the atmosphere. Bleed-hole 37 may provide access to atmosphere through an orifice in lower flange 9, or by any other suitable means, since it is not contemplated that the invention be restricted to any particular form of giving said exhaust air access to the atmosphere.

It will now be evident that a cushioning effect may be secured on this stroke by the compression of the weight of air trapped within the end of cylinder 10 which abuts the lower flange. The trapped air is obtained, of course, by the engagement of disc 31b with the flat surface of the flange 9, which blocks port 19.

It will also be evident that a separate cushioning adjustment exists for each of the compression cups 27a and 27b. For instance, by changing the position of the nut 33a, changes are wrought in the cushioning effect on that side of the piston assembly. The initial volume of trapped air which must be compressed by the piston assembly prior to reaching the end of the stroke controls the cushioning on that side of the piston assembly.

Since the force needed in pulling the actuating rod downward to close the movable jaw is substantially greater than that necessary for the upward stroke, which merely repositions the jaws, the need for cushioning on opposite sides of the piston assembly is obvious.

More particularly, where suflicient air pressure is used to overcome the substantial resistance of a tough limb, the piston assembly will accelerate very rapidly towards the upper end of the cylinder 10, immediately upon severing the last fiber of said limb.

In this case, the cushioning required to decelerate the piston and extract suflicient kinetic energy therefrom to obviate destructive impact will be substantially absorbed on the return stroke of the piston. It is believed that the advantage of thus providing cushioning means on each side of the piston assembly, and making it possible to absorb dissimilar deceleration rates on each side of said piston, are sufliciently obvious to render further detailed description unnecessary.

Although, therefore, a specific embodiment of this invention has been shown and described, it will be understood, of course, that it is merely illustrative and that certain changes and modifications may be made therein without departing from the scope and spirit of this invention as defined in the appended claims.

What is claimed is:

1. In an air-powered pruning shears of the character described, an upper flange having an axial bore and a flat inner surface provided with a port for passage of air therethrough; a lower flange having a flat inner surface provided with a port for passage of air therethrough; a cylinder eflectively secured to and adjoining said flat inner surfaces of said flanges to effectively communicate with said ports; an actuating rod, provided with a threaded portion and slidably disposed within said axial bore and said cylinder; a spacer-disc positioned transversely on said actuating rod; a first and a second flexible cup mounted respectively on opposite sides of said spacer-disc to engage the inner walls of said cylinder; a first and a second compression cup provided each with an axially extending shoulder and adapted to threadedly engage said actuating rod and abut both sides of said spacer-disc to clamp said first and second flexible cups thereto; a first and a second sleeve mounted upon said actuating rod to abut said first and second compression cups respectively; a first and a second flat disc mounted transversely upon said first and second sleeves respectively and adapted to engage one of said fiat inner surfaces of said flanges at the end of each stroke to prevent further passage of exhaust air from said cylinder; a first and a second nut threadedly engaging said actuating rod and abutting said disc; a first spring mounted concentrically with said first sleeve between said first disc and said first compression cup, and a second spring mounted similarly upon said second sleeve between said second disc and said second compression cup; and, means to supply compressed air alternately to opposite sides of said cylinder to effect reciprocation of said actuating rod whereby obstruction of said ports in said flanges and compression of said springs effectively minimizes impact.

2. In a pneumatic pruner of the character described, an upper flange having an axial bore and a flat inner surface provided with a port, a lower flange having a fiat inner surface and provided with a port, a cylinder, means securely affixing said cylinder between said flat inner surfaces to communicate with said ports, an actuating rod slidably mounted in said axial bore and cylinder, a pair of flexible cups mounted to resiliently engage the inner walls of said cylinder, a spacer-disc mounted to radially separate said flexible cups, a pair of compression cups provided with oppositely extending axial shoulders and mounted to threadedly engage said actuating rod to tightly abut said spacer-disc and clamp said flexible cups thereto, a pair of sleeves mounted upon said actuating rod to abut opposite sides of said compression cups, a pair of flat discs each mounted upon one of said sleeves to close one of said ports on alternate strokes of said actuating rod to terminate passage of air from said cylinder; a first and a second nut, each to threadedly engage said rod and abut the axially outermost surface of one of said discs, a pair of coil springs, each mounted between one of said compression cups and one of said flat discs to bias said flat disc axially outward, and, means to supply compressed air alternately to opposite ends of said cylinder to reciprocate said actuating rod.

3. In a pneumatic pruner provided with an actuating rod, a cylinder for enclosing a portion of said rod, means aflixed to said rod to resiliently engage and divide said cylinder into two variable-volume compartments, and means to supply compressed fluid alternately to said compartments to impart motion to said rod located therebetween, the improvement which comprises means including a port for exhausting residual air from each of said compartments during the reduction in the volume thereof caused by said motion, and individual adjustable resiliently biased disc means mounted on opposite sides of said dividing means to alternately block each of said ports at a predetermined initial volume to provide a cushion of compressible fluid.

References Cited in the file of this patent UNITED STATES PATENTS 

